JPH03159905A - Production of sodium hydrosulfide and production equipment - Google Patents

Abstract

PURPOSE:To continuously obtain highly purified sodium hydrosulfide from raw material gas containing hydrogen sulfide without generation of environmental pollution by combining a first absorbing tower having a bubble tower structure and a second absorbing tower having a storage tank storing a large amount of an absorbing solution. CONSTITUTION:Raw material gas 11 containing hydrogen sulfide is continuously introduced into a first absorbing tower 1 having a bubble tower structure from a lower part of said tower and brought into contact with an absorbing solution 18 continuously introduced from an upper part of the first absorbing tower 1 and containing caustic soda, etc., in an amount lesser than a stoichiometric amount required for reacting whole hydrogen sulfide contained in the raw material gas 11, then sodium hydrosulfide is generated and recovered. On the other hand, gas 12 containing residual hydrogen sulfide is taken out from the upper part of the first absorbing tower 1 and introduced into the second absorbing tower 2 having a storage tank 3 storing a large amount of the absorbing solution, then brought into contact with excess amount of the absorbing solution. Thus, a part of the absorbing solution 18 used in the second absorbing tower 2 is fed to the first absorbing tower 1 and simultaneously a fresh absorbing solution 14 is supplied to the second absorbing tower 2 from outside of said system.

Description

[Detailed description of the invention] a. Purpose of the invention [Field of industrial application] The present invention provides a method for producing high-purity sodium hydrogen sulfide that is substantially free of sodium sulfide and at the same time reducing hydrogen sulfide contained in exhaust gas and released. It is something to do.

[Prior Art] A method for producing sodium bisulfide by absorbing hydrogen sulfide into an aqueous solution of caustic soda or sodium sulfide has been known for some time.

For example, in Japanese Patent Publication No. 37-6501, hydrogen sulfide contained in petroleum cracked gas is absorbed into caustic soda waste liquid produced during the petroleum refining process to produce sodium hydrogen sulfide.

In such a manufacturing method, from the viewpoint of protecting the environment, it is necessary to suppress the release of hydrogen sulfide accompanying the exhaust gas.

For this reason, as seen in Special Publication No. 38-11951,
Several absorption towers filled with waste caustic soda liquid are installed at appropriate positions, and gas containing hydrogen sulfide is fed into the liquid in the first absorption tower, and the unabsorbed gas is transferred to the next absorption tower in order. A batch type system in which the liquid saturated with hydrogen sulfide is extracted from the first-stage absorption tower and replaced with new liquid, and this absorption tower is used as the last stage, and the second-stage absorption tower is used as the first stage and operated in the same manner. Several absorption towers filled with treatment equipment or Raschig rings are installed, and gas containing hydrogen sulfide is continuously fed from the lower part of the first absorption tower and sequentially sent to the next stage through the exhaust port at the top of the tower. A continuous treatment device has been proposed in which waste caustic soda liquid is continuously dripped from the top of the last stage absorption tower, and a portion is sequentially sent to the previous stage absorption tower while circulating in a bomb, and sodium hydrosulfide is taken out as a solution from the first stage absorption tower. ing. In Japanese Patent Publication No. 59-26902,
When producing a sodium hydrogen sulfide aqueous solution by reacting hydrogen sulfide with a caustic soda aqueous solution while separating and removing carbon dioxide contained in the hydrogen sulfide, an absorption tower filled with a first bubble tank, a second bubble tank, and a Raschig ring are connected in series. A method is shown in which the produced liquid is extracted from the bottom of the first bubble tank.

However, in these methods, it was not possible to avoid the contamination of caustic soda or sodium sulfide into the product sodium hydrogen sulfide.

Sodium hydrosulfide is used in a wide range of fields, including reduction of dyes and intermediates, vulcanization, hair removal of leather, desulfurization of viscose rayon, sulfur dyeing, pulp digester, and flotation aid. Although commercially available sodium hydrogen sulfide contains a considerable amount of sodium sulfide as an impurity, it does not pose any particular problem for the above-mentioned uses.

However, when trying to use it as a raw material for the synthesis of organic sulfur compounds, product quality problems arise due to the formation of by-products, so there is a need for high-purity sodium hydrogen sulfide that does not substantially contain sodium sulfide. It has become.

Caustic soda (NaO■) or soda sulfide (Nat
The reaction to produce sodium hydrogen sulfide (NaSH) by reacting S) with hydrogen sulfide (H.S) is 2NaOH + Has- + NaJ + 2HiO
(11Mass + His” 2NaSH
(21) That is, in the reaction with caustic soda, it is said that equation (1) first proceeds to produce sodium sulfide, and then soda sulfide is converted to sodium hydrogen sulfide by equation (2).

(When formula 11 and formula (2) are combined, formula (3) is obtained.

NaOH + Has-I NaSH
+ HtO (31 When the starting material is soda sulfide, sodium hydrogen sulfide is produced according to equation (2).

When producing sodium bisulfide by reacting caustic soda and/or sodium sulfide with hydrogen sulfide, in order to produce high-purity sodium bisulfide that does not contain sodium sulfide and to avoid releasing unreacted hydrogen sulfide, Caustic soda and/or raw materials
Alternatively, it is necessary to keep the ratio of supply amounts of sodium sulfide and hydrogen sulfide constant. If there is an excess of caustic soda or sodium sulfide, the reaction of formula (3) or (2) will not be completed, and caustic soda or soda sulfide will be mixed in the product.
On the other hand, if hydrogen sulfide is in excess, hydrogen sulfide will remain in the exhaust gas and be released outside the system.

The supply ratio of soda and hydrogen sulfide is calculated from equations (2) and (3) by l. O mol/mol. Since this ratio changes when the soda supply flow rate, soda concentration, raw material gas supply flow rate, and raw material hydrogen sulfide concentration fluctuate, it is difficult to maintain the ratio accurately at 1.0.

Conventional methods require three or more absorption towers in order to reduce the amount of hydrogen sulfide emitted along with the exhaust gas and to produce sodium hydrogen sulfide with few impurities, resulting in high production costs and a complicated flow scheme. It has to be complicated. Furthermore, it cannot be said that this method can sufficiently cope with fluctuations in the raw material gas flow rate, the hydrogen sulfide concentration of the raw material gas, the soda supply flow rate, and the soda concentration.

[Problems to be Solved by the Invention] The present invention is directed to producing high-purity sodium hydrogen sulfide that does not contain sodium sulfide when producing sodium hydrogen sulfide by reacting caustic soda and/or sodium sulfide with hydrogen sulfide, and It is an object of the present invention to provide a method and apparatus for producing sodium hydrogen sulfide that can reduce the release of unreacted hydrogen sulfide to the outside of the system.

B. Structure of the Invention [Means for Solving the Problems] The method for producing sodium hydrogen sulfide according to the present invention consists of: (1) continuously introducing a raw material gas containing hydrogen sulfide from the lower part of a first absorption tower having a bubble column structure; 1 Continuously introduced from the upper part of the absorption tower and containing an amount of caustic soda and/or soda sulfide in an amount smaller than the stoichiometric amount required to react the entire amount of hydrogen sulfide contained in the continuously introduced raw material gas. contact with the absorbing liquid containing sodium hydrogen sulfide to produce sodium hydrogen sulfide, and continuously discharging the reaction product liquid containing sodium hydrogen sulfide from the bottom of the first absorption tower,
■The gas containing residual hydrogen sulfide discharged from the top of the first absorption tower is introduced into the second absorption tower, which has a storage tank that holds a large amount of absorption liquid inside or outside the tower, so that the gas containing residual hydrogen sulfide is contained in the raw material gas. The hydrogen sulfide removed is brought into contact with an absorption liquid containing caustic soda and/or sodium sulfide in an excess amount than the stoichiometric amount required to react the entire amount of hydrogen sulfide, and the gas from which hydrogen sulfide has been removed is discharged from the top of the second absorption tower. ◎ A part of the absorption liquid used in the second absorption tower is supplied as the absorption liquid used in the first absorption tower, and ◎ Absorption liquid containing fresh caustic soda and/or sodium sulfide is supplied from outside the system to the second absorption tower. It is characterized by being additionally supplied to the absorption liquid used in

In addition, the soda hydrogen sulfide manufacturing apparatus according to the present invention has a feed pipe (line 11) for raw material gas containing hydrogen sulfide at the bottom, a discharge pipe (line 19) for the reaction product liquid at the bottom, and an unreacted gas discharge pipe (line 19) at the top. line 12), a first absorption tower (1) with a bubble column structure equipped with a supply pipe (line 18) at the top that supplies a part of the absorption liquid used in the second absorption tower below, a gas discharge pipe at the top (Line 13), below which is an inlet pipe (Line 12) for gas discharged from the top of the first absorption tower, and has a storage tank (3) that holds a large amount of absorption liquid inside or outside the tower. It is composed of a second absorption tower (2) and a supply pipe (line 14) for additionally supplying fresh absorption liquid as absorption liquid to the second absorption tower, and is sulfurized in the unreacted gas discharged from the top of the first absorption tower. A mechanism for detecting the hydrogen concentration and controlling the amount of absorption liquid supplied from the second absorption tower to the first absorption tower so that the value becomes a constant value (concentration meter 2--11 collected liquid supply control valve 22), A control mechanism for discharging the absorption liquid of the first absorption tower to the outside of the system so that the absorption liquid of the first absorption tower maintains a constant level (level gauge 23, discharge valve 24), and a tower of the second absorption tower. Fresh absorption liquid is added to the second tank so that the liquid level in the storage tank installed inside or outside the tower remains constant.
Control mechanism for additionally supplying absorption liquid to the absorption tower (level gauge 2)
5-1-1 Additional absorption liquid supply valve 26) is provided.

The present invention will be specifically described below using the accompanying drawings. Note that in the attached drawings, a heat exchanger for removing reaction heat is omitted to avoid complexity.

FIG. 1 shows one example of the embodiment of the present invention, in which the first absorption tower 1 is a bubble tower, with a feeding pipe (line 1 1) for feed gas containing hydrogen sulfide at the bottom, and a reaction product at the bottom. A discharge pipe (line 19) for discharging the liquid, a discharge pipe (line 12) for discharging unreacted gas at the top, and a supply pipe (line 18) for supplying a part of the absorbed liquid of the second absorption tower 2 at the top. There is.

The second absorption tower 2 is a packed tower having a storage tank 3 for holding a large amount of absorption liquid containing caustic soda and/or sodium sulfide in the lower part of the tower, and is equipped with a gas discharge pipe (line l1 1 3) at the top. An inlet pipe (line 12...a line from the unreacted gas discharge pipe of the first absorption tower) for gas discharged from the top of the first absorption tower is provided below the gas discharge pipe.

Furthermore, a supply pipe (line 14) for additionally supplying fresh absorption liquid as absorption liquid to the second absorption tower merges with the absorption liquid circulation line 17 from the storage tank, and passes through line 15 to the second absorption tower. guided by.

Part of the absorption liquid used in the second absorption tower, that is, storage tank 3
A portion of the absorption liquid retained in the absorption liquid is supplied to the first absorption tower through line 18.

It is necessary to use a bubble column as the first absorption column 1. In other words, in the first absorption tower, since the content of caustic soda and/or sodium sulfide in the absorption liquid is small, the reaction rate is controlled by the residence time of the liquid, so using a packed tower or tray stage is more effective than using a bubble column. This requires a very high absorption tower height, which is not practical.

The type of the second absorption tower may be a bubble column, a packed column, or a tray column, and it may be selected depending on the allowable pressure loss of the system and the characteristics of gas-liquid contact performance. We will explain the case using .

Line 1l from the bottom of the first absorption tower 1 having a bubble column structure
A raw material gas containing more hydrogen sulfide is continuously introduced, and is brought into contact with an absorption liquid containing caustic soda and/or sodium sulfide that is continuously introduced from the upper part of the first absorption tower through line 18 to produce sodium hydrogen sulfide. The reaction product liquid containing sodium hydrogen sulfide is continuously discharged from the bottom of the first absorption tower through a bomb 5 and a line 19 to produce a product.

The amount of caustic soda and/or sodium sulfide contained in the absorption liquid that is continuously introduced into the first absorption tower is such that the entire amount of hydrogen sulfide contained in the raw material gas that is continuously introduced into the first absorption tower reacts. It is necessary to use an amount smaller than the stoichiometric amount required for this, preferably about 0.5 to 0.75 times the amount.

The method of controlling the amount of absorption liquid supplied to the first absorption tower is based on the above conditions, that is, the stoichiometric amount required to react the entire amount of hydrogen sulfide contained in the raw material gas introduced into the first absorption tower. Any method can be adopted as long as it can reduce the amount of absorption liquid to the first absorption tower. By controlling the supply amount, it is possible to respond in a short time to sudden changes in the raw material gas supply flow rate, raw material hydrogen sulfide concentration, etc., and it is easy to stably obtain high-purity sodium hydrogen sulfide.

Specifically, the concentration of hydrogen sulfide in the gas discharged from the first absorption tower is measured by a concentration meter 21, and the absorption liquid supply control valve 22 is operated via a control device such as a cascade control, and the hydrogen sulfide is discharged. The hydrogen sulfide in the gas may be controlled to be maintained at a predetermined concentration.

A liquid level gauge 23 is installed in the first absorption tower, and a discharge valve 24 is operated to control the discharge amount of the liquid absorbed by the first absorption tower so that the liquid level is maintained at a predetermined value.

By controlling in this manner, unreacted caustic soda or sodium sulfide is not present in the aqueous solution discharged from the bottom of the first absorption tower, and a highly pure sodium hydrogen sulfide aqueous solution is obtained.

Gas containing residual hydrogen sulfide is discharged from the top of the first absorption tower through a line 12, but this gas is introduced into the second absorption tower 2, which has a storage tank 3 that holds a large amount of absorption liquid, to Hydrogen sulfide is brought into contact with an absorption liquid containing caustic soda and/or sodium sulfide in an excess amount than the stoichiometric amount required to react the entire amount of hydrogen sulfide contained in the gas, and hydrogen sulfide is transferred from the top of the second absorption tower through line 13. The removed gas is discharged, and a part of the absorption liquid used in the second absorption tower is supplied as an absorption liquid used in the first absorption tower via bomb 4 and line 18, and fresh caustic soda and/or Alternatively, the absorption liquid containing sodium sulfide is additionally supplied to the absorption liquid used in the second absorption tower via line 14 and line 15.

The remainder of the absorption liquid used in the second absorption tower is passed from the storage tank 3 to the bomb 4 and line 17, and is then transferred from the line 15 together with the absorption liquid containing fresh caustic soda and/or sodium sulfide supplied from the line 14. The gas is circulated to the upper part of the second absorption tower 2 and brought into contact with the gas containing residual hydrogen sulfide introduced from the line 12.

1 5 A liquid level gauge 25 is installed in the absorption liquid storage tank 3 of the second absorption tower,
The absorption liquid additional supply valve 26 is operated so that the liquid level is maintained at a predetermined value, and fresh absorption liquid is introduced from the line 14 into the second absorption tower.

In this case, the amount of caustic soda and/or soda sulfide contained in the absorption liquid that comes into contact with the gas in the second absorption tower is such that the entire amount of hydrogen sulfide contained in the raw material gas that is continuously introduced into the first absorption tower is reacted. It is necessary to use an amount in excess of the stoichiometric amount necessary to achieve the desired effect, preferably 1.5 times or more.

The average amount of fresh caustic soda and/or sodium sulfide in the absorption liquid supplied from line 14 is theoretically enough to react the entire amount of hydrogen sulfide contained in the raw material gas continuously introduced into the first absorption tower. Since the amount is 1.0 times the required stoichiometric amount, the amount of caustic soda and/or sodium sulfide in the circulating absorption liquid that is extracted from the storage tank 3 and reintroduced into the upper part of the second absorption tower is If the amount is at least 0.5 times the stoichiometric amount required to react the entire amount of hydrogen sulfide contained in the raw material gas continuously introduced into the absorption tower, the total amount is at least 1 6 1.5 times. It can be done.

By controlling in this way, there is almost no unreacted hydrogen sulfide in the gas discharged from the top of the second absorption tower through the line 13, and there is no possibility of adverse effects on the environment.

In addition, fresh caustic soda and/or water supplied from line 14
Alternatively, the absorption liquid containing sodium sulfide may be introduced into the storage tank 3.

The capacity of the storage tank 3 provided inside or outside the second absorption tower is:
Although it varies depending on the fluctuation range of the hydrogen sulfide concentration in the raw material gas and the control method for fresh caustic soda and/or sodium sulfide solution supplied from outside the system, it is necessary to supply at least the amount of hydrogen sulfide contained in the raw material gas for 1 hour. It is necessary to have a capacity that can hold the absorption liquid necessary for absorption.

By doing so, it is possible to cover fluctuations in the supply flow rate of caustic soda and/or sodium sulfide, their concentration, the raw material gas supply flow rate, and the raw material hydrogen sulfide concentration, thereby facilitating stable operation. If it is less than this value, there is a risk that hydrogen sulfide will leak into the exhaust gas within a short time when the amount of hydrogen sulfide in the raw material gas fluctuates.

FIG. 2 shows another example of the embodiment of the present invention, which has exactly the same configuration as the embodiment of FIG. 1 except that the storage tank 3 is provided outside the second absorption tower 2. The operating method is exactly the same as that shown in Figure 1. Note that line 16 is the second
This is a liquid feeding line from the absorption tower 2 to the external storage tank 3.

FIG. 3 shows another example of the embodiment of the present invention,
The second absorption tower 2 is a bubble tower, and itself also serves as a storage tank 3 for the absorption liquid.

In this case, the gas containing residual hydrogen sulfide discharged from the top of the first absorption tower is blown from the lower part of a large amount of absorption liquid stored in the second absorption tower and rises in the absorption liquid in the form of bubbles. , even without circulating the absorption liquid, the gas containing residual hydrogen sulfide contains an excess amount of caustic soda and/or soda sulfide than the stoichiometric amount required to react the entire amount of hydrogen sulfide contained in the raw material gas. It comes into contact with the containing absorbent liquid. Of course, the absorption liquid may be circulated. Other operating methods are exactly the same as those shown in FIG.

FIG. 4 shows the second
A case is shown in which an apparatus having a structure in which the absorption tower 2 is installed on top of the first absorption tower 1 is used. Note that the line 20 is a circulation line for the first absorption tower absorption liquid used at the start of operation. The circulation line for the liquid absorbed by the first absorption tower is not shown in FIGS. 1, 2, and 3.

Further, in order to remove the reaction heat, a heat exchanger may be installed in the line 20, and this circulation line may be used during operation.

It is preferable that the raw material gas does not substantially contain a substance such as carbon dioxide that reacts with caustic soda and/or the sodium sulfide solution, and that the partial pressure of hydrogen sulfide is 0.1 kg/cm"A or more. Caustic soda conforms to the JIS standard. It is preferable to use the highest quality soda specified in 1. Waste soda used for abatement, etc. can also be used as long as it does not substantially contain impurities other than sodium hydrogen sulfide and caustic soda.

19 [Example] The effectiveness of the present invention was verified using an apparatus having the flow scheme shown in FIG.

As the first absorption tower, the inner diameter is 1.0 m, and the effective liquid layer height is 2.0 m.
A bubble column having a packed bed of 5/8 inch ball rings with an inner diameter of 0.5 m and a bed height of 2.0 m was used as the second absorption column.

1.6 m of 26 wt% caustic soda aqueous solution was placed in the first absorption tower.
', 0 at the bottom of the second absorption tower and at the absorption liquid storage tank 3, respectively.
2m'. After charging 3.0 m3 of the aqueous solution, the valve on the absorption liquid supply line l8 to the first absorption tower and the first
The valve on the absorption tower absorption liquid discharge line 19 was closed, the first absorption tower pump 5 and the second absorption tower pump 4 were started, and the caustic soda solution was circulated in each absorption tower. Next, a raw material gas containing hydrogen sulfide was introduced from the raw material gas line l1.

When sodium sulfide is no longer detected in the circulating liquid of the first absorption tower and almost all of the soda in the circulating liquid of the second absorption tower has been converted to sodium sulfide, the circulating liquid of the second absorption tower is 1 into the absorption tower and through lines 14 and 15 a fresh 26% by weight aqueous caustic soda solution (specific gravity 1.2).
6) At the same time as the introduction into the second absorption tower at 0.440 m'/h was started, the sodium hydrogen sulfide aqueous solution was extracted through line 19. The temperature of line 15 and line 18 was adjusted to 50°C.

The supply conditions and composition of the raw material gas were as follows.

Flow rate: 1105 Nm'/h Pressure: 2.2 Kg/cm' G Temperature: 50°C Group rules: I{2 S: 7.3 mo1%, H2: 84.8 mo1%, H2 0: 3.9 mo1%, CH4: 4 ．． Omo1% Circulation amount of second absorption tower absorption liquid through line 17 is 0.99
5 m'/h, and the amount of soda contained in the absorption liquid that is continuously introduced into the first absorption tower reacts with the entire amount of hydrogen sulfide contained in the raw material gas that is continuously introduced into the first absorption tower. When the steady state is achieved by controlling the O to be 5 times the stoichiometric amount required for 1st of
The amount of liquid discharged from the absorption tower was 0.545 m3/h. In addition, the amount of caustic soda and sodium sulfide contained in the absorption liquid that comes into contact with the gas in the second absorption tower is controlled by the chemical reaction necessary to cause the entire amount of hydrogen sulfide contained in the raw material gas that is continuously introduced into the first absorption tower to react. It was about three times the stoichiometric amount.

Further, the amount of absorption liquid held in the storage tank inside the second absorption tower and outside the tower was enough to absorb 3.6 hours of supply of hydrogen sulfide in the raw material gas.

The sodium hydrogen sulfide concentration of 0.545 m3/h of the sodium hydrogen sulfide aqueous solution obtained from line 19 in this way is 31.4.
The sodium sulfide concentration was less than 100 ppm by weight (specific gravity of the aqueous solution: 1.18).

In addition, H. The S concentration was analyzed, but it was not detected.

Next, the supply amount of fresh caustic soda aqueous solution is 0.400 m'
/h, and the operation continued without changing other conditions except for changing the amount of liquid discharged from the first absorption tower accordingly.
Even after 4 hours, the analysis value of sodium sulfide in the product was 10.
It was less than 0 ppm by weight and no hydrogen sulfide was detected in the exhaust gas from the second absorption tower.

As is clear from the above, according to the control method of the present invention, good operation is possible even in the event of fluctuations.

When the amount of fresh caustic soda supplied was changed in the same way without installing an absorbent storage tank, the sodium sulfide concentration in the product after 3 hours was less than 100 ppm by weight, but the concentration of sodium sulfide was not discharged from the second absorption tower. The gas contains 280 pp by volume of hydrogen sulfide.
m was detected.

In addition, the amount of caustic soda and/or sodium sulfide contained in the absorption liquid that is continuously introduced into the first absorption tower reacts with the entire amount of hydrogen sulfide contained in the raw material gas that is continuously introduced into the first absorption tower. When the amount was set at 0.9 times the stoichiometric amount required for this, the sodium sulfide concentration in the product was 980 ppm by weight.

23 In addition, the amount of caustic soda and/or sodium sulfide contained in the absorption liquid that comes into contact with the gas in the second absorption tower is large enough to react with all the hydrogen sulfide contained in the raw material gas that is continuously introduced into the first absorption tower. The amount should be 1.2 times the required stoichiometric amount,
Supply amount of fresh caustic soda from O, 440m3/h to 0
．． When the speed was changed to 400 m'/h, the sodium sulfide concentration in the product after 24 hours was less than 100 ppm by weight.
100 ppm by volume of hydrogen sulfide was detected in the gas discharged from the second absorption tower.

C. Effects of the invention A continuous method that allows mass production, with a simple flow scheme that uses only two absorption towers, produces sodium hydrogen sulfide that does not substantially contain sodium sulfide, and at the same time reduces sulfide that is released along with the exhaust gas. The amount of hydrogen can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an embodiment of the present invention, FIG. 2 is a diagram showing another embodiment, FIG. 3 is a diagram showing another embodiment, and FIG. 4 is a diagram showing an example of the embodiment of the present invention. FIG. 9A is a diagram showing a case where an apparatus having a structure in which the second absorption tower is installed on top of the first absorption tower is used in the embodiment described above.

Claims (1)

[Claims] 1(a) A raw material gas containing hydrogen sulfide is continuously introduced from the lower part of a first absorption tower having a bubble column structure, and the raw material gas containing hydrogen sulfide is continuously introduced from the upper part of the first absorption tower, and the continuous contact with an absorption liquid containing caustic soda and/or sodium sulfide in an amount smaller than the stoichiometric amount required to react the entire amount of hydrogen sulfide contained in the raw material gas introduced as The reaction product liquid containing sodium hydrogen sulfide is continuously discharged from the bottom of the first absorption tower, and (b) a large amount of gas containing residual hydrogen sulfide is discharged from the top of the first absorption tower into the tower or outside the tower. An excess amount of caustic soda and/or soda sulfide than the stoichiometric amount required to react the entire amount of hydrogen sulfide contained in the raw material gas by introducing it into a second absorption tower having a storage tank for holding an absorption liquid of (c)
A part of the absorption liquid used in the second absorption tower is supplied as the absorption liquid used in the first absorption tower, and (d) the absorption liquid containing fresh caustic soda and/or sodium sulfide is supplied from outside the system to the second absorption tower. A method for producing sodium hydrogen sulfide, which is characterized in that it is additionally supplied to the absorption liquid used. 2 The amount of caustic soda and/or sodium sulfide contained in the absorption liquid that is continuously introduced into the first absorption tower reacts with the entire amount of hydrogen sulfide contained in the raw material gas that is continuously introduced into the first absorption tower. 2. The method for producing sodium hydrogen sulfide according to claim 1, wherein the amount is 0.5 to 0.75 times the stoichiometric amount required for. 3 The amount of caustic soda and/or sodium sulfide contained in the absorption liquid that comes into contact with the gas in the second absorption tower is necessary to react the entire amount of hydrogen sulfide contained in the raw material gas that is continuously introduced into the first absorption tower. 2. The method for producing sodium hydrogen sulfide according to claim 1, wherein the amount is 1.5 times or more the stoichiometric amount. 4 The amount of absorption liquid held in the absorption liquid storage tank is 1
2. The method for producing sodium hydrogen sulfide according to claim 1, wherein the amount includes caustic soda and/or sodium sulfide necessary to react the hydrogen sulfide contained in the supplied amount over an hour. 5 At the bottom is a feed pipe for raw material gas containing hydrogen sulfide, at the bottom is a discharge pipe for reaction product liquid, at the top is an unreacted gas discharge pipe, and at the top is a supply pipe for supplying a portion of the absorption liquid used in the second absorption tower below. The first absorption tower has a bubble column structure equipped with a tube, a gas discharge pipe is provided at the top, and a gas inlet pipe below which is discharged from the top of the first absorption tower is provided. A second absorption tower having a storage tank for holding the absorption liquid and a second absorption tower for storing fresh absorption liquid.
It is composed of a supply pipe for additionally supplying the absorption liquid to the absorption tower, and detects the hydrogen sulfide concentration in the unreacted gas discharged from the top of the first absorption tower. 1. A mechanism for controlling the amount of absorption liquid supplied to the absorption tower;
A control mechanism for discharging the absorption liquid of the first absorption tower to the outside of the system so that the absorption liquid of the first absorption tower maintains a constant level, and a control mechanism that maintains the liquid level of the storage tank provided inside or outside the second absorption tower. An apparatus for producing sodium hydrogen sulfide, comprising a control mechanism for additionally supplying fresh absorption liquid as absorption liquid to a second absorption tower so as to maintain a constant liquid level.